1. Field of the Invention
The present invention relates to a heat exchanger and a method of producing the same, and more particularly to a heat exchanger for use in a cryogenic refrigerator, such as a reversed Stirling cycle refrigerator, a Gifford-MacMahon cycle refrigerator, a pulse tube refrigerator, and the like.
2. Description of the Related Art
One typical example of known heat exchangers comprises a regenerative matrix for allowing a gas to flow therethrough and having a heat conductivity, a heat capacity, and a wide contact surface held in contact with the gas, and is thus adapted to exchange heat energy between the regenerative matrix and the gas while the gas is passing through the regenerative matrix. The heat exchanger is generally utilized as a regenerator for a cryogenic refrigerator.
A typical cryogenic refrigerator of this type, for example, a pulse tube refrigerator, is shown in FIG. 32 as comprising a gas cylinder 1, a regenerator 2, a pulse tube 3, a reciprocating piston 4, an orifice valve 5, and a buffer tank 6.
The gas cylinder 1 is formed with a chamber having the reciprocating piston 4 movably received therein and divided into two spaces one of which defines a hermetical sealed gas chamber 1a having a center axis and a gas flow port opened to the regenerator 2. The regenerator 2 comprises a pair of heat exchanging portions 2a and 2b and a regenerative matrix portion 2c interposed between the pair of heat exchanging portions 2a and 2b. The heat exchanging portion 2a of the regenerator 2 is mechanically connected to the gas cylinder 1 through the gas flow port of the gas chamber 1a of the gas cylinder 1.
The pulse tube 3 is formed with a gas chamber 3a and has a first longitudinal end portion mechanically connected to the heat exchanging portion 2b of the regenerator 2, and a second longitudinal end portion opposite to the first longitudinal end portion and mechanically connected to the buffer tank 6 through the orifice valve 5. The gas chamber 1a of the gas cylinder 1, the regenerator 2, and the gas chamber 3a of the pulse tube 3 therefore collectively define a hermetically sealed closed system.
The gas chamber 1a of the gas cylinder 1, the gas chamber 3a of the pulse tube 3, and the buffer tank 6 are filled with a refrigerant gas. The regenerator 2 is formed with a plurality of gas flow passageways for allowing the refrigerant gas to flow between the gas cylinder 1 and the pulse tube 3 therethrough with a large gas contact area surface to be held in contact with the refrigerant gas. The regenerative matrix 2c of the regenerator 2 is adapted to exchange the heat energy with the contacted refrigerant gas.
The reciprocating piston 4 is reciprocated along with the center axis of the gas cylinder 1 to have the refrigerant gas in the gas chamber 1a of the gas cylinder 1 repeatedly compressed and expanded and to allow the compressed and expanded refrigerant gas to flow between the gas chamber 1a of the gas cylinder 1 and the gas chamber 3a of the pulse tube 3 through the gas flow passageways of the regenerator 2.
The buffer tank 6 is designed to cooperate with the orifice valve 5 to regulate a pressure in the gas chamber 3a of the pulse tube 3, thereby causing a pulsatory motion of compressed and expanded gas in the gas chamber 3a of the pulse tube 3.
The reciprocating motion of the reciprocating piston 4 and the pulsatory motion of gas flow are repeated at a predetermined cycle, but performed at different phases from each other while the refrigerator operates. The pulsatory motion of gas flow in the gas chamber 3a of the pulse tube 3 is phase shifted by one fourth of the cycle, i.e., a phase angle of 90 degrees with respect to the reciprocating motion of the reciprocating piston 4.
The refrigerator is repeatedly operated in accordance with the following four processes consisting an isothermal compression process, an isovolumetric heat radiating process, an isothermal expansion process, and an isovolumetric heat absorbing process.
In the isothermal compression process, the refrigerant gas is compressed in the gas chamber 1a of the gas cylinder 1, and the heat energy is transferred from the refrigerant gas to the heat exchanging portion 2a of the regenerator 2. Accordingly, the heat exchanging portion 2a of the regenerator 2 is heated while the refrigerant gas is cooled.
In the isovolumetric heat radiating process, the heat energy is radiated from the heat exchanging portion 2a of the regenerator 2 to the outside of the refrigerator 2. The cooled refrigerant gas flows from the gas chamber 1a of the gas cylinder 1 to the gas chamber 3a of the pulse tube 3 through the regenerator 2. The regenerative matrix 2c of the regenerator 2 is operated to exchange the heat energy with the refrigerant gas, when the refrigerant gas is transferred between the gas chamber 3a of the pulse tube 3 and the gas chamber 1a of the gas cylinder 1 through the regenerator 2. In this case, the heat energy is transferred from the regenerator 2 to the refrigerant gas.
In the isothermal expansion process, the refrigerant gas is expanded in the gas chamber 3a of the pulse tube 3, and the heat energy is transferred from the heat exchanging portion 2b of the regenerator 2 to the refrigerant gas. Accordingly, the heat exchanging portion 2b of the regenerator 2 is cooled while the refrigerant gas in the gas chamber 3a of the pulse tube 3 is heated.
In the isovolumetric heat absorbing process, the heated refrigerator gas flows from the gas chamber 3a of the pulse tube 3 to the gas chamber 1a of the gas cylinder 1 through the regenerator 2. The heat energy is transferred from the regenerator 2 to the refrigerant gas. The refrigerator repeatedly performs the aforesaid processes.
A conventional regenerator constituting the heat exchanger of the above type is shown in detail in FIG. 33. The regenerator of the heat exchanger comprises a cylindrical casing 7 and a plurality of regenerative plates 8. The cylindrical casing 7 is formed with a chamber 7a having an opened end.
Each of the regenerative plates 8 is produced by modeling a mesh plate after a predetermined pattern. As a result, the regenerative plates 8 thus constructed have a tendency to be irregular in size and shape, thereby causing the heat exchanger to be irregular in relationship between the neighboring two regenerative plates 8 in the cylindrical casing 7. For this reason, it is difficult for the heat exchanger to obtain a desired efficiency of heat exchanging between the regenerative plates 8 and the gas.
In the process of producing the heat exchanger, the regenerative plates 8 are inserted into the cylindrical casing 7 through the opened end of the chamber 7a of the cylindrical casing 7 one by one by hand to form into a regenerative heat exchanging unit 9 including thousands of regenerative plates 8. Therefore, the heat exchanging unit 9 is produced to be laborious in work and management of the large number of regenerative plates 8, thereby taking much time of manufacturing process and bringing a high cost.
The heat exchanger of another type is disclosed in U.S. Pat. No. 5,746,269, filed Aug. 13, 1993 and assigned to the assignee of the present invention in which each of the regenerative plates is made of a thin metal plate formed with a plurality of holes by etching. This type of heat exchanger has an advantage in a flexible design of the regenerative plates as well as making the regenerative plates uniform in size and shape. As a result, the heat exchanger can effectively exchange the heat energy between the regenerative plates and the gas. However, this type of heat exchanger has still a drawback to be encountered in that the heat exchanger comprises a large number of regenerative plates inserted in the gas casing one by one by hand, thereby taking much time of manufacturing process and bringing a high cost.
In the aforesaid heat exchanger, the neighboring two regenerative plates 8 are held in directly contact with one another so that the regenerative plates 8 in the heat exchanger define as a whole a heat transmission path in parallel relationship with the gas flow passageways. In consequence, the heat exchanger further has a drawback to be encountered in that the heat energy is liable to transfer between the neighboring two regenerative plates 8, thereby causing a loss in the heat conductivity.